So, Holly seems to be allergic to worming pills The first time we wormed her (not long after we got her, so at the start of the year) she vomited (only once), but we thought maybe she just ate something else that made her sick (she does eat a lot of rubbish) and it was just a coincidence. So last night we wormed her (she eats a lot of cat, chicken and horse poop so she really did need wormed). She was sick for the rest of the evening. Non-stop vomiting until all that was left was water. She looked to sad, she just sat in the corner looking sick and shivering . Poor puppy. The only times she has ever vomited was after being wormed so I'm pretty sure it's not a coincidence now. She's alright today. I tried to give her just a small breakfast of chicken. But she was hungry and demanded more so she seems completely recovered. So how do I figure out what part of medication she is allergic to so we can avoid this? She also reacted to the pain killers she had after her speying surgery (I think it was called Fentenol or something) it was a patch bandaged to her leg and we had to have it removed because it made her all hyper and crazy, she couldn't sleep or relax at all, she just ran around constantly (the vet said she should be sleepy after the surgery and if anything the drug should also make her more doppy, but it did the opposite for Holly. The vet really didn't want to remove it at first because she said little dogs need the painkiller, but it was doing more harm than good) and that was the day after surgey, we thought she was going to pop her stitches or something. But she was fine once we got the patch removed and she calmed down. I don't really know about allergies in dogs, so is it common for dogs to have drug allergies? and are these two things (Fentenol and worming pill) common? and are there any other drugs that we should avoid as likely to also make her sick?